The last few weeks of public appearances have been particularly intense for the favorite British royal family - the Duke and Duchess of Cambridge and their two infant children, Prince George and Princess Charlotte - and the consequent fashion frenzy around their outfits, style statements that have immediate economic repercussions on the clothing industry amounting to billions of dollars.

The Cambridge Effect in action: Every item Kate Middleton, Princess Charlotte and Prince George wore for the queen's birthday celebration became highly-sought by shoppers around the world Photo: Ben A. Pruchnie/Getty Images

The “Cambridge Effect” (more on that in a moment) means that any article of clothing any of them wears - sorry, William, mainly Kate Middleton and the kids - for a public function or a special photo sells immediately. You must have noticed that many of the media at the public events attended by the Duke and Duchess of Cambridge include in their coverage the fashions she or her children are wearing, with their prices, where to purchase them or how to order them from the internet.

Whatever Princess Charlotte and Prince George wear in any season instantly becomes sought after by parents Photo: ALP/MediaPunch

The phenomenon is so prevalent and its impact on the fashion industry now so important that the ‘Duchess of Cambridge Effect” (also known as the "Kate Effect," and the "Duchess Effect") deserves its own entry in Wikipedia, which defines Kate’s as “the trend-effect that Catherine Duchess of Cambridge has on others from cosmetics to sales of coral-colored jeans” and it cites a Newsweek report estimating that The Kate Effect is worth more than £1 billion to the British fashion industry.

Catherine's Anita Dongre dress during a cricket match on the April India visit was in such demand that the designer's factory had to suspend all other production to fill its orders Photo: Chris Jackson/Getty Images

An apt example was the frantic rush for the dresses she wore during hers and William's visit to India and Bhutan in April. The printed dress by Anita Dongre that she wore for a cricket game was such a success that the designer’s factory temporarily was forced to shift production from all its other models exclusively to produce the dress in order to meet the sudden and enormous demand.

George's outfit has triggered a copycat frenzy among parents Photo: Duke and Duchess of Cambridge.org

Princess Charlotte's bow disappeared from store shelves following this photo taken by her mother Photo: British Monarchy

At one year old, Princess Charlotte, already a fashion icon worth billions of pounds to the fashion industry Photo: British Monarchy

Her young kids already are called ‘icons of fashion’ due to their marketing power. Literally every article of their clothing seen publicly, from a small pin in Princess Charlotte’s hair to the socks sported by the little prince, become objects of utmost attraction for millions of shoppers. Like their mother, every appearance of Prince George or Princess Charlotte ripples through the industry as parents from around the world start looking for the same dresses, boys' shorts, cardigans, shoes, hair bows, and tights. The brands that create them and the stores that sell them experience massive online traffic surges and orders.

Prince George's robe for his encounter with President Obama became a fashion phenomenon Photo: British Monarchy

The sales for this quilted jacket increased by 440% after the photo appeared Photo: British Monarchy

A report by Brand Finance quoted in the Fashionista says that the little "princess effect" is worth a staggering £3.2 billion to the British fashion industry. In an article entitled “The Princess Charlotte Effect Is Over One Billion Dollars Stronger Than The ‘Prince George Effect',” the blog reports that “Prince George's economic contribution is only about £2.4 billion. Though, this discrepancy is no fault of George's own: the boys' fashion market is simply smaller than the girls.”

The most recent case concerns the manufacturer of the pink shoes the little princess wore for her debut on the balcony in Buckingham Palace on June 11, when the one-year old joined her brother and parents to be cheered by their subjects as they watched Queen Elizabeth's birthday parade.

The retailer that made the quilted jacket Prince George wore for his first day of school enjoyed a sales increase of 440%.

Even more impressive: The statistics around the white monogrammed robe the little Prince wore to greet a bemused President Obama during his last visit to Kensington Palace. At its peak, sales hit one every second after the first photos of the American president kneeling to talk to the robe-clad toddler went viral.

Demand for the item rocketed off the charts and My First Years, the robe maker, said that its inventory sold out in the 60 seconds following the robe's identification in the photo. That equaled a 750% hike in sales, with traffic to its website up by 500% - and half the orders sourced in the United States.

Catherine's hats mark the world of headwear design and anxiously anticipated at any formal event Photo: Chris Jackson/Getty Images

The British press has a blast publishing such staggering numbers and betting on which effect is more astonishing, Prince George's or his sister's.

In a recent column about “How Prince George’s Style Became Big Business,” royal expert Tom Sykes says that the “Kate Effect” has gained such proportions that “cynical profiteers have taken to snapping up her latest coat dress or hat on Amazon, and reselling the items on
eBay before they have even been delivered.”

Since Kate Middleton’s taste is for the more traditional, impeccably matched with modern touches, fashion designers are producing lines that reflect that trend to respond to the interest of the many wannabe Kates seeking to emulate her style.

Her taste for the classic reflects in the clothes she chooses for her toddlers. “For children’s wear, she is definitely into retro looking outfits which is adorable for toddlers and is becoming a real fashion trend thanks to her,” Cecile Reinaud, the founder of Séraphine, the maternity brand Kate wore during her pregnancy, told Sykes.

“Kate likes to mix styles on George, so for example she will put him in a classic pair of boys shorts but with a cute and fun jumper," she noted. "She’ll team a classic cashmere cardigan with a pair of crocs shoes to give a contemporary twist.”